ELK GROVE, CA - The criminal case that will likely put a child molester behind bars for life began with the photograph of a garbage can.

Among the many pornographic pictures of a single child taken by Bradley Dayley, 40, was one with the image of a 90-gallon plastic garbage container in the background marked with the words "Elk Grove California."

Elk Grove police Det. Kevin Papineau said the pictures landed on his desk in 2009 after being discovered by the National Center for Missing and Exploited Children from an overseas source.

"Receiving the pictures, all we knew was it happened in Elk Grove," Papineau recalled. "From there we had to try to use every detail we could to narrow it down."

Papineau organized a canvass of every elementary school in Elk Grove and in neighboring communities. Nobody recognized the girl in the photographs.

So Papineau began looking closely at the homes in the pictures for any distinctive architecture or other unique markers.

After driving through Elk Grove neighborhoods for nearly a month, Papineau found what he was looking for on a street near the southern edge of the city.

A split fence board, curiously placed in the middle of a side yard fence, perfectly matched the one in the pedophile's photograph.

The house was owned by Dayley during the time the pictures were taken. A search of his new home a few miles away uncovered other photographs and videotape of the same child.

Investigators said the child, a relative, had been molested for four years beginning at age 9. Evidence led to a second molest victim who was 16 when the sexual assaults began.

Dayley pleaded guilty this week to multiple child molestation charges and will be sentenced next month to more than 60 years in state prison.

Dayley still faces federal charges relating to the production and possession of child pornography that could effectively extend the prison term to life.

Investigators said the molestations continued up until the time Dayley was arrested.

A news release from the Sacramento County District Attorney's Office hailed Papineau as a hero for his tenacious police work in catching the predator.

Papineau modestly shrugged off the accolade, preferring to share the credit with others who helped in the investigation.

But the veteran police officer admitted it was the most fulfilling case in which he'd ever been involved.

"The day we found (the victim) and saw she was the real girl after looking at pictures of her for a whole month, that was the most rewarding thing I've ever experienced in law enforcement," Papineau said.